Excerpt from Pitted Keratolysis

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Background

Pitted keratolysis is a skin disorder characterized by crateriform pitting that primarily affects the pressure-bearing aspects of the plantar surface of the feet and, occasionally, the palms of the hand as collarettes of scale. The manifestations are due to a superficial cutaneous bacterial infection.

Pitted keratolysis has gone through several name changes. It was described initially in the early 1900s as keratoma plantare sulcatum, a manifestation of yaws. It was identified in the 1930s as a unique separate clinical entity, and the name was changed to keratolysis plantare sulcatum. The current name, pitted keratolysis, describes the clinical presentation well.

Pathophysiology

Pitted keratolysis is caused by a cutaneous infection with Micrococcus sedentarius¹ (now renamed to Kytococcus sedentarius), Dermatophilus congolensis,² or species of Corynebacterium and Actinomyces. Under appropriate conditions (ie, prolonged occlusion, hyperhidrosis, increased skin surface pH), these bacteria proliferate and produce proteinases that destroy the stratum corneum, creating pits.³ K sedentarius has been found to produce 2 keratin-degrading enzymes. They are protease P1 (30 kd) and P2 (50 kd).⁴ The malodor associated with pitted keratolysis is presumed to be the production of sulfur-compound by-products, such as thiols, sulfides, and thioesters.

In 2006, foot odor without pitted skin changes was discovered to be from isovaleric acid produced by Staphylococcus epidermidis, a normal skin flora.⁵

Frequency

United States

Pitted keratolysis occurs worldwide. It can be seen in both tropical and temperate environments. A study of 142 homeless men in the Boston area revealed that 20.4% of 142 examined patients had pitted keratolysis.⁶

International

Prevalence rates have ranged from 1.5% of 4325 Japanese industrial workers to 2.25% (11 of 490 subjects randomly evaluated) in New Zealand. In the tropical military setting, where heat, humidity, and boots combine to produce a microenvironment that predisposes to this disease, prevalence rates are much higher. Of the 387 volunteer soldiers evaluated in South Vietnam, 53% had pitted keratolysis. Recently, in Britain, 25 of 184 examined athletes had pitted keratolysis. In 341 paddy field workers in costal South India, 42.5% had pitted keratolysis.⁷

Mortality/Morbidity

No mortality is associated with pitted keratolysis. However, the excessive foot odor from this disorder may be socially unacceptable. Pitted keratolysis may be symptomatic; producing secondary painful feet, which can limit function. In 2005, in Turkey (East region), a study of dermatologic manifestations in 88 hepatitis B surface antigen carriers compared with 84 controls demonstrated a significantly higher prevalence of oral lichen planus and pitted keratolysis. The mechanism is unknown and further studies are needed to confirm this association.⁸

Race

No race predilection is reported.

Sex

Theoretically, both males and females should be affected; however, most written case reports or studies have involved male patients.

Age

Pitted keratolysis can affect patients of any age.

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